The present invention relates to a solid-state image pickup device and a method of producing such a device. In particular, the present invention relates to a technique which is effective in application to a technique for producing a solid-state image pickup device using an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) sensor.
A solid-state image pickup element (image sensor) such as a CMOS sensor or a CCD sensor is used in optical devices such as digital cameras. Light (a beam) led by an optical lens forms an image on the surface (light receiving face or image pickup face) of a solid-state image pickup element (solid-state image pickup chip). The image is converted to an electric signal by cells (pixels) of the solid-state image pickup element, and taken out as image information.
On the other hand, the distance from a lens (optical lens) becomes long in an image center of the solid-state image pickup element which coincides with an optical axis of the optical lens and in a peripheral part. The so-called curvature of field aberration occurs and the lens is out of focus, resulting in a blurred image and a lowered resolution. As a method for eliminating such curvature of field aberration, a method of curving the light sensing face of the solid-state image pickup element (sensor chip) in a concave form so as to conform with the curvature of field is known (for example, JP-A-10-108078, JP-A-2004-349545 and JP-A-2004-146633).
According to a technique disclosed in JP-A-10-108078, the back of a solid-state image pickup chip is adhered to one face of a flexible elastic plate, and the curvature of the elastic plate is adjusted to adjust the curvature of the light sensing face of the solid-state image pickup chip.
According to a technique disclosed in JP-A-2004-349545, a planar image pickup element (Si having a thermal expansion coefficient of 4 ppm/K) and a planar member (invar having a thermal expansion coefficient of 2 ppm/K) that is different in thermal expansion coefficient from the image pickup element are stacked and bonded to each other in a high temperature state and then cooled to the normal temperature. The light sensing face of the image pickup element is curved to take a concave shape by a difference caused in shrinkage quantity between the image pickup element and the planar member due to the cooling. Thereafter, the image pickup element in the curved state is mounted on a substrate.
According to a method disclosed in JP-A-2004-146633, when joining a solid-state image pickup element to a printed circuit board of a material that is larger in thermal expansion coefficient than a material of the solid-state image pickup element via a projection electrode, the light sensing face of the image pickup element is curved to take a concave shape by a difference caused in thermal expansion coefficient between the printed circuit board and the image pickup element due to the cooling action after the heating and joining.
On the other hand, the conventional solid-state image pickup apparatus typically has a structure incorporating a solid-state image pickup element in a package called cer-DIP (for example, JP-A-2003-243635). A semiconductor device (solid-state image pickup device) disclosed in JP-A-2003-243635 has a structure in which a top opening of a package main body formed of ceramics is sealed with a lid formed of a glass plate. An element disposing region of a bottom part which is an internal bottom of the package main body is curved, and a solid-state image pickup element is stuck fast to and joined to the curved face.